Propriedades ópticas de aerossóis na atmosfera de Natal/Brasil medidas por meio de um fotômetro solar da rede AERONET

Abstract

The study of atmospheric aerosols contributes to the understanding of radiative forcing and global warming. In addition, aerosols may influence atmosphere chemistry, visibility, acid rain, human health and precipitation. Since 2016, Natal, capital of Rio Grande do Norte, Brazil, has a solar photometer (CIMEL) of the RIMA-AERONET network that can identify the presence of biomass burning aerosols and desert dust from Africa. For this identification, it is aimed to characterize the optical properties of these aerosols present in the atmosphere of Natal (RN). The data available by AERONET, at level 1.5, Version 3, provide information on microphysical characteristics such as Optical Aerosol Depth (AOD), Ångström Coefficient (α), Single Scattering Albedo (SSA), Asymmetry Factor (g), Complex Refractive Index (N), Volume Size Distribution (VSD) and Precipitable Water. The data collection period was from August 2017 to March 2018. Aerosols were classified based on global climatologies and their optical properties were described. The observations of satellites and the local LIDAR were verified in the course of a day for a case study. In addition, backward trajectories were modeled with the HYSPLIT model to identify the predominant origins of the air masses. Aerosols present in the atmospheric column of Natal showed monthly means of AOD in the range of 0.10 to 0.15 with data representation of ~40%, monthly means of α between 0.6 and 0.8 with representation above 30%, bimodal VSD with dominant coarse mode, SSA about 0.80, real part around 1.500, imaginary part ranging from 0.0125 to 0.0437 and g above 0.74. The Precipitable Water accompanied the increase of AOD with a weak correlation (R = 0,43). The classification showed mixed aerosols (60.40%), marine aerosols (30.69%) and mineral dust (8.91%). The backward trajectories identified that in about 51% of the cases the continental aerosols origined from the Africa.